Fix mid-call silence: keep momentum after acknowledgments

A caller gave their insurance; AVA replied with a bare acknowledgment ("staff
will verify your coverage") and stopped, with no follow-up question. Both sides
then waited -> dead air (pipeline idle, no GPU/LLM activity, matching flat
memory/wattage). Caller had to break the silence with "what questions do you
have?". Root cause: the one-sentence brevity rule made AVA end a booking turn on
a dead-end statement.

Fix: prompt now requires, until the booking is complete, that every turn end
with the next question — acknowledgment + next question in the same turn (e.g.
insurance ack -> immediately ask day/time). Verified 4/4. Documented in CLAUDE.md.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

bot.py

@@ -138,7 +138,11 @@ SYSTEM_PROMPT = (
     "  5. WRAP UP — recap the booking as a REQUEST in one warm sentence (for example, 'I've "
     "noted your request to come in tomorrow afternoon at our Kendall office'), make clear a "
     "staff member will call back to CONFIRM it, then ASK IF THERE IS ANYTHING ELSE you can help "
-    "them with. Only once they are all set, give the closing below.\n\n"
+    "them with. Only once they are all set, give the closing below.\n"
+    "KEEP MOMENTUM: until the booking is complete, ALWAYS end your turn with the next question "
+    "you still need answered. Never reply with only an acknowledgment and then stop — for "
+    "example, after noting insurance, in the SAME turn go straight on to ask the preferred day "
+    "and time. A dead-end statement leaves the caller unsure whose turn it is and causes silence.\n\n"
     "Stay truthful and within your limits:\n"
     "- Use ONLY the facts below for addresses, phone numbers, insurance, and services. Never "
     "make any of these up.\n"